The invention relates to an electrical contact element and, in particular, to surface mounting of electrical contact elements to a connecting area of electrically conducting material situated near the edge of a substrate.
For mutually detachable electrical connection of circuit parts, plug and socket connections have been used on a large scale. In principle, one can distinguish between two types of connections based upon their construction. In one type of connection devices, the contact elements are accommodated in a separate, sometimes specially shaped housing. In the other type, the contact elements are mounted directly onto a substrate without such housing. The present invention is concerned with the latter type of construction.
Surface mounting is increasingly replacing the older insertion methods for electrically connecting of circuit elements to a substrate or a printed wiring board. In surface mounting, the connecting ends of the circuit elements are connected to small connecting areas on one face of a substrate. The respective components may be mounted on the connecting areas, inter alia, by means of various soldering techniques and/or with electrically conducting adhesive.
Problems, however, arise in surface mounting a row of contact elements, for example, near an edge of a substrate or a printed wiring board. One problem involves correctly positioning the contact elements with respect to each other and with respect to the edge of the substrate.
If the contact elements are mutually displaced or if they are displaced with respect to the edge of the substrate, it will not be possible, or it will be possible only with great difficulty, to introduce a row of plug-in contact elements into a corresponding row of receiving openings or receiving contact elements. In this connection, it should be borne in mind that, in practice, plug-and-socket connections having twenty contact elements or more with a pitch distance of 1.27 mm or less are used. A relatively small error in positioning one or a few contact elements may result in a circuit board provided with complex electronic circuits, being unusable in practice. Moreover, the reliability of the plug-and-socket connection will not be favorably influenced if undesirable mechanical forces are exerted on one or more contact elements.